1. Field of Invention
The present invention relates to a method and device for uncoupling a self-propelled truck from a carrying truck which is coupled therewith via a coupler, at a predetermined uncoupling point.
2. Description of Prior Art
Most of large industrial factories and storehouses are equipped with some self-propelled trucks and carrying trucks to be coupled therewith as an indoor automated transfer means for transferring goods and articles to a destination in production lines or a storage section.
In general, the self-propelled truck has a self-driving mechanism comprising driving wheels, a motor operatively connected to the driving wheels, and a photo-sensitive guidance and control system, so that the truck moves by itself moves along a given path labelled by a light reflecting tape. This self-propelled truck is provided with a device for coupling and uncoupling it with a carrying truck which is adapted fro carrying articles thereon.
A known device for coupling the self-propelled truck is constructed by a pair of male and female engagement elements, one of them being at the self-propelled truck and another of them provided at the carrying truck. In most cases, those two separate engagement elements require a connecting pin for locking their mutual engagement to complete the coupling between the self-propelled and carrying trucks, which needs manual insertion and removal of the connecting pin by workers in the coupling steps.
In this construction, there has been a coupling/uncoupling device as known from the Japanese Patent Laid-Open Pub. No. 4-328008, which features the use of a male engagement pin at a carrying truck, a vertically movable female engagement member at a self-propelled truck, and an uncoupling stand member at a given uncoupling point on the path along which the two trucks move. In brief, according thereto, the carrying truck is automatically coupled with the self-propelled truck at a predetermined coupling point, with the male engagement pin of the former truck being brought to engagement with the female engagement member of the latter truck, and on the other hand, when the two coupled trucks reach the uncoupling point, the vertically movable female engagement member is raised, riding on the uncoupling stand member, for disengagement from the engagement pin.
Particularly, with regard to the uncoupling system in this prior art, it has been found defective that even after uncoupling from the self-propelled truck, the carrying truck will move on under its inertia force and overrun beyond the uncoupling point to stop at an undesired point. Therefore, it is difficult to cause the uncoupled carrying truck to be stopped precisely at the uncoupling point, and this will be true even though the point may be relocated for the inertia overrun degree because the floor on which the truck moves is not always flat, including an uneven and sloped areas.
Moreover, the same inertia overrun effect also involves a possibility for the uncoupled carrying truck to be re-engaged with the self-propelled truck. In other words, at the uncoupling point, before the the female engagement member, which has been raised by the stand member, is lowered to a home horizontal position, the carrying truck is being still moved with the self-propelled truck, with the result that the female engagement member is again engaged with the male engagement pin, hindering the uncoupling operation.
Additionally, the uncoupling stand member erected on the floor impairs a working space and lowers a safety conditions on the floor.